The present invention relates to a medical instrument, comprising:
an elongated shaft having a distal end and a proximate end;
a movable tool disposed at said distal end of said shaft;
a handle disposed at said proximal end of said shaft;
a force transmitting element extending along said shaft and movable in a first and an opposite second movement direction, said force transmitting element being operatively interconnected between said tool and said handle for converting a movement of said handle into a movement of said tool.
An instrument of this kind is known from DE 43 03 544 A1.
This known instrument is an applicator for applying hemostatic clips. Although the present invention is described hereinafter using the example of a clip applicator of this kind, the invention is nevertheless not limited to a medical instrument in the form of such a clip applicator, but rather can also be used with other instruments, as will be described below.
A clip applicator generally has, at the distal end of the shaft, a tool in the form of two jaw parts that are preloaded resiliently into a spread position. The two jaw parts can be pressed together, by advancing a sleeve, out of their spread position into a closed position. The sleeve is joined to an force transmitting element in the form of a push bar that in turn is joined at the proximal end to the movable grip element of the handle of the instrument. The V-shaped or U-shaped clips are arranged in the shaft, serially one behind another, in a magazine. By way of an advance mechanism, the particular clip located closest to the jaw parts is slid between the spreadapart jaw parts. Actuation of the handle moves the force transmitting element (and thus the sleeve) axially in the distal direction, thus pushing the jaw parts together out of their spread position and thereby closing the clip that is located between the jaw parts by deformation.
Clips of this kind are used, for example, to close off blood vessels or for surgical sutures.
When a clip applicator of this kind is used, the problem arises that the clip currently located between the jaw parts can fall out of the jaw parts if, during the operation of closing the jaw parts, the handle is released or the manual force for actuation of the handle is reduced before the clip has been completely closed onto the corresponding tissue or onto the vessel. In particular if the handle is preloaded by spring force into its starting position, the result of releasing the handle during the closing operation would be that the force transmitting element would move back into its starting position; as a result, the jaw parts would open, so that the clip, not yet closed, would fall out of the jaw parts. If a clip is lost in a patient""s body, this can have devastating consequences if the loss is not noticed.
This problem cannot be eliminated even if defined click-stop positions, for example by way of a toothed rack, are provided on the handle or the force transmitting element, since the jaw parts can open at least a little way, corresponding to the distance between two click-stop positions, when the handle is released, so that in this instance as well the clip that is located between the jaw parts and is not completely closed can fall out. The surgeon must therefore continuously take care, during the closing operation, not to reduce his manual force on the handle so as not to interrupt the closing operation before the clip is completely closed.
The problem described above occurs, however, not only specifically with a clip applicator but also with other medical instruments in which a movable tool is present that can be moved back and forth in two opposite directions. Such an instrument can, for example, be a forceps for grasping tissue, which has two jaw parts that are closed so as to grasp tissue between the jaw parts for removal from the body. What occurs here is the comparable problem that the jaw parts can open again when the handle is released, so that the tissue being grasped can fall out as the forceps is withdrawn from the body; this must absolutely be avoided as long as the jaw parts are still in the body. Further examples of instruments in which similar problems occur are needle holders and sponge holders.
It is therefore an object of the invention to develop an instrument of the kind cited initially in such a way in the event of a reduction in manual force during actuation of the handle, or in the event the handle is released, the movable tool cannot unintendedly move back opposite to the actuation direction.
According to the present invention, this object is achieved in the case of the instrument cited initially in that steplessly acting locking means coact with said force transmitting element for steplessly locking the movement of said force transmitting element in said first movement direction, whereas said locking means allow free movement of said force transmitting element in said opposite second movement direction.
Because of the steplessly operating locking means provided according to the present invention, the at least one movable tool can be immobilized in any desired position so as not to move opposite to the actuation direction, while the actuation direction is not impeded. If the handle is released or if there is any reduction in manual force, the tool remains in the position most recently attained. In the case of a clip applicator, because of the stepless locking system the jaw parts cannot unintendedly open again if the handle is released or if there is a reduction in manual force, thus preventing the clip located between the jaw parts from falling out if the clip is not yet applied in completely closed fashion to the vessel or tissue. In the case of a grasping forceps as well, any loss of the grasped tissue inside the body is prevented. The same is true for a needle holder or sponge holder. Because the locking means coact with the force transmitting element, an additional result is an advantageously simple design of the locking mechanism. The force transmitting element remains stationary in any axial position and thus, as soon as the handle is no longer being actuated, also immobilizes the tool in the position it has just reached.
In a preferred embodiment, the locking means are configured so that they coact with the force transmitting element with clamping force in the locked direction.
This feature is advantageous because it makes possible, in a physically simple fashion, a locking system for the movement of the force transmitting element in the locking direction that operates reliably and steplessly, i.e. acts at any desired point in the movement travel of the force transmitting element.
In a further preferred embodiment, the locking means can be brought into engagement with the force transmitting element by spring force.
The advantage here is that the preloading of the locking means by the spring force makes possible reliable automatic engagement with the force transmitting element.
In a further preferred embodiment, means are provided for disengaging the locking means from the force transmitting element in order to move the force transmitting element back in the first movement direction previously locked by the locking means.
The means for disengaging the locking means thus result in cancellation of the locking effect of the locking means, so that the force transmitting element can be moved back into its starting position, after which the instrument is once again ready for the next actuation.
It is particularly preferred in this context if the means for disengaging the locking means are moved along with the force transmitting element, and in a predefined first position coact automatically with the locking means in order to disengage the latter.
It is advantageous in this context that the unlocking of the force transmitting element is also derived automatically from the movement of the force transmitting element, with no need for a manual action in order to unlock the force transmitting element. The predetermined first position at which the means for disengaging the locking means coact with the locking means can advantageously be, for example, the end position of the force transmitting element in which the at least one tool has reached its actuation end position. In conjunction with a clip applicator, this is preferably the position of the force transmitting element in which the jaw parts and thus the clip that is to be applied are completely closed, so that then, by releasing the handle, the force transmitting element can be moved back into the starting position if the handle is correspondingly preloaded by spring force into its starting or rest position.
In this connection, it is further preferred if the means for disengaging the locking means hold the locking means in their non-locking position during the movement of the force transmitting element back in the previously locked first movement direction and, in a predetermined second position, release the locking means so that the locking means can once again coact lockingly with the force transmitting element.
This advantageously ensures that as the force transmitting element is moved back, the locking means are reliably held in their non-locking position, so that the force transmitting element can be moved back into the starting position again in freely movable fashion and without resistance to movement.
Whereas the aforementioned embodiments result in the creation of a generally automatic mechanism for locking, unlocking, relocking, etc. the force transmitting element, it is also preferred if the means for disengaging the locking means are manually actuable.
It is advantageous here that unlocking of the force transmitting element can be performed at any desired movement positions of the force transmitting element between the two axial end positions.
In a further preferred embodiment, the locking means have an axially stationary locking element, at least partially surrounding the force transmitting element circumferentially, that is tiltable into the locking position and vice versa about a pivot axis running eccentrically with respect to the force transmitting element.
This specific embodiment creates a mechanism of advantageously simple design for locking the one movement direction of the force transmitting element, in particular in conjunction with the preloading of the locking means by spring force, by the fact that the locking element, by tilting about the pivot axis running outside the force transmitting element, can be brought into engagement with the latter and out of engagement with it again.
It is further preferred if there is arranged on the locking element, on the side of the force transmitting element located opposite to the pivot axis, a compression spring which tilts the locking element in the direction of the first movement direction to be locked, so that at least one edge of an opening of the locking element comes into clamping contact with the force transmitting element by jamming.
The compression spring provided at this point preloads the locking element against the force transmitting element. Specifically, the compression spring tilts the locking element, with a strong lever effect, in the direction of the locked first movement direction of the force transmitting element, as a result of which the locking element can jam with and thus clamp the force transmitting element. Even if a force is acting on the force transmitting element attempting to move the force transmitting element in the locked movement direction, for example in the case of a spring-loaded handle, any such force even further reinforces the clamping effect between the locking element and the force transmitting element, thus achieving a reliably operating locking action, of immediate onset, on the force transmitting element.
In a further preferred embodiment, the means for disengaging the locking means have a disengagement element that is arranged on the force transmitting element and projects radially beyond it and moves along with the force transmitting element, such that in order to disengage the locking element, in the first position the disengagement element comes into contact against the locking element, as a result of which the latter is tilted out of the tilted locking position into the non-locking position.
This feature creates a disengagement element of simple design for automatic unlocking of the force transmitting element in the aforementioned predetermined first position, with no need for a manual action in order to disengage the locking means.
It is further preferred if the means for disengaging the locking means have a holding element that comes into contact against the locking element after tilting into the non-locking position and holds it in the non-locking position until the force transmitting element has been moved back, opposite to the previously locked movement direction, into the second position.
After the locking element has been tilted into the non-locking position, the holding element assumes the function of the disengagement element when the latter is moved back, along with the force transmitting element, into the starting position. The holding element automatically prevents the locking element from clamping against the force transmitting element, so the latter can be moved in freely movable fashion back into the starting position.
In this context, the holding element has an oblique shoulder onto which the disengagement element runs as the force transmitting element is moved back, thus causing the holding element to move out of contact with the locking element.
The oblique shoulder configured on the holding element, which coacts with the disengagement element as it is moved back into the starting position in order to bring the holding element out of contact with the locking element so that the locking element can once again coact lockingly with the force transmitting element, advantageously results in a mechanism for locking and unlocking the force transmitting element that makes do with few parts, locking and unlocking being brought about solely by the movement of the force transmitting element between the two axial end positions.
In the case of the instrument according to the present invention, provision can advantageously be made either for the force transmitting element to be locked in the proximal movement direction when the force transmitting element is being operated by pushing to actuate the tool, or for the force transmitting element to be locked in the distal movement direction if the force transmitting element is operating by pulling.
As already mentioned, the invention can also be advantageously provided for a forceps, in particular a grasping forceps, for an applicator for applying one or more clips, or for a needle holder or sponge holder.
Further advantages are evident from the description below and the appended drawings.
It is understood that the features recited above and those yet to be explained below can be used not only in the respective combination indicated, but also in other combinations or in isolation, without leaving the context of the present invention.